Thermal responsive device



F. R. HIGLEY 2,290,963

THERMAL RESPONSIVE DEVICE July 28, 1942.

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.Patented JulyL-S, 1942 THERMAL RESPONSIVE DEVICE Frank R. Higley, Cleveland Heights, Ohio, assignor to The Bryant Heater Company, Cleveland, Ohio, a corporation of Ohio Application April 19,l1941, 'Serial No. 389,401

4 Claims.

This invention relates to improvements in compensated thermostatic elements, that is to say thermostaticelements whichare independent of ambient temperature and dependent for actuation upon theapplication of localized heat. Thermostatic elements of this character are commonly employedin connection with pilot controls for duid burners, being responsive to heat from the pilot to operate a valve, an electric switch or other shiftable control member.

One of the objects ofthe invention is the provision of a thermostatic element of this kind which may be formed from regular stock material at a minimum of expense.

Another object is the provision of a thermostatic element4 of the character described which shall have a relatively large exure under the influence of applied heat and shall thereby be adaptable to a 'widened range of applications.

^ Other objects and features of novelty will appear as I proceed with the description of those embodiments of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawing in which: Fig. l is a plan view of a thermostatic element embodying the invention;

Fig. 2 is a side elevation of thesame, portions being shown in longitudinal section;

Fig. 3 is a view similar to Fig. 1 but showing the element under iiexure, the degree of flexure being exaggerated in order to more fully illustrate the invention;

Fig. 1 is a transverse section taken on the line t 4,--4 0I.' Fig. 2;

Fig. 5 is a transverse section of a modified form of the invention;

Fig. 6 is a plan view of another modified form; and I Fig. 7 is a detail sectional view taken substantially on the line 'I-l of Fig. 6.

ompensated thermal elements as heretofore produced and rused havel been constructed in some cases of flat` plates or strips of material provided with .perforations extending lengthwise of the element so as to interfere with the transmission of heat crosswise ofthe stri-p. Such an element flexes in a direction parallel to its greater cross-sectional dimension and is adapted to perform relatively heavy work, but it has a stroke of very limited extent. The thermostatic element of the present invention on the other hand has a relatively long stroke, but its flexure takes place in a plane at right angles to its greatest cross-sectional dimension and the -element is therefore able to exert less force than the nat strip elements now in more or less common use.

In Figs. l, 2, and 3 of the drawing I have shown a thermostatic element I0 formed from a lengthl of solid rod which is circular in cross-section. The circular cross-section is utilized partially because it is a common commercial prodacut is taken from a point opposite the first cut. In this manner tapered ends I2 are formed at the extremities-of the slot, thereby eliminating the weak spots which would otherwise be pressented by the junction of the slotted and solid parts, and reducing possible breakage. With respect to cross-sectionalv dimensions, the slot II is shown centered midway of the rod, but it may be desirable in some instances to offset it from the median position. Its length may be varied. The parallel members formed by the slot are marked 9 in the drawing.

Points at which heat ina-y be applied te' the rod on one side of the slot are indicated .by the arrows I3 in Fig. 3. However, a single flame may be used instead of two names, or the number may be increased to three or more. Qbviously,variations in the length of slot used may call for a variation in the'number of names em- Ilployed. In any case to get maximum deflection of the rod it should be heated more or less evenly along one of the walls opposite the slot. The number and size of the flames will naturally be regulated to produce a maximum effect throughout the length of the slotted portion.

One end of the rod is fixed as indicated at I4 in the drawing, a. set screw being illustrated for the purpose at I5. The other end of the rod may be formed for a convenient connection with some suitable control element.' As shown herein, I may eut away opposed surfaces to form -a at extremity I6 and may bore a hole therethrough for a pivot pin or the like, not shown, to constitute part of the control connections. When heat is applied as at points I3 in Fig. 3 to one member of the rod, that member expands and puts a curve into that portion of the rod, which accomplishes a deflection of the free end as indicated to an exaggerated degree in the drawing. A

Fig. 4 shows a cross-section of a rod like that of Figs. 1 to 3, inclusive. 'I'he member or wall portionon each side of the slot is a segment of a circle. The mass in each segment is equally divided by an axis A1 which is closer to the inner wall of the segment than to its outermost point.

In Fig. 5 where the cross-section of a rectangular` rod is shown, the masses in the members on opposite sides of the slot are divided equally by axis lines A2 and A2. If the width of the rod of Fig. 5 is the same as the diameter of the rod of Fig. 4, the lines A2 will be further apart than the lines A1. The mean exure of each wall portion takes place in what are originally planes through these lines Al and A2. Since the distance between the lines A1 is less than that between the lines A2, the

ilexure of the round rod will be sharper or on a or if preferred, the projection may be drilled toreceive rivets 20 or the like extending through aligned holes in the rod walls, as illustrated in the drawing.

Having thus described my invention, I claim: 1. A thermal responsive device comprising a metal rod of round cross section having a longitudinal slot therethrough forming two parallel members, whereby flexure will result from a difference in temperature between the two said members.

2. A thermal responsive device comprising a metal rod having a'longitudinal slot therethrough forming two parallel members, whereby flexure will result from a difference in temperature between the two said members, said slot extending through a portion only of the rod length and leaving unslotted a substantial portion thereof, whereby movement resulting from said iiexure may be multiplied by the unslotted portion of the rod.

3. A thermal responsive device comprising a metal rod having a solid portion and a portion provided with a longitudinal slot, whereby the application of heat to the rod on one side of said slot will cause flexure of the rod, the junction of said solid and slotted portions having a gradually varying cross-sectional area, whereby the localization of stresses at the said junction will be minimized.

4. A thermal responsive device comprising a metal rod having a longitudinal slot therethrough extending from one end of the rod and terminating short of the other end leaving two parallel members on opposite sides of the slot, mounting means lling the slot between the outer ends of said parallel members, and fastenings extending through said members and said mounting means, whereby the device is rigidly supported and iiexure will result from a difference in temperature between the two members.

Y FRANK R. HIGLEY. 

